Just a curiosity question. Remember when in class groupwork the professor would divide people up into groups of a certain number (n)?
Some of my professors would take a list of n people one wants to work with and n people one doesn't want to work with from each student, and then magically turn out groups of n where students would be matched up with people they prefer and avoid working with people they don't prefer.
To me this algorithm sounds a lot like a Knapsack problem, but I thought I would ask around about what your approach to this sort of problem would be.
EDIT: Found an ACM article describing something exactly like my question. Read the second paragraph for deja vu.
To me it sounds more like some sort of clique problem.
The way I see the problem, I'd set up the following graph:
It is then a matter of partitioning the graph into cliques of size n. (Assuming the number of students is divisible by n)
If this was not possible, I'd probably let the first constraint on the edges slip, and have edges between two people as long as neither of them explicitly says that they don't want to work with the other one.
As for an approach to solving this efficiently, I have no idea, but this should hopefully get you closer to some insight into the problem.